Use of an infrared light-emitting source as a light source for exposure enables use of a bright safelight, and is advantageous from the view point of readiness in handling. For this reason, proposals have been made on silver halide photographic papers spectrally sensitized to the infrared region.
Such photographic papers can be exposed to light to form an image by utilizing an image forming process of, for example, the so-called scanner system.
In the image forming process according to the scanner system, an original is scanned, an image signal resulting therefrom is converted to light, to which a silver halide photographic light-sensitive material is exposed, and thus a negative image or positive image corresponding to the image on the original is formed. There are various types of recording apparatus in which the image forming process according to the scanner system is practically employed. As light sources for the recording in such scanning recording apparatus, a glow lamp, a xenon lamp, a mercury lamp, a tungsten lamp, a light-emitting diode and so forth have been hither to used. All of these light sources, however, involve practical problems that they give a weak output and have a short lifetime. As a means for solving such problems, there are scanners in which a coherent laser light source such as a helium-neon laser, an argon laser or a helium-cadmium laser is used as a light source in the scanner system. These can give a high output, but have the problems that the apparatus must be large, they are expensive, they require a modulator, and also they have inferior handling characteristics because the safelight for a light-sensitive material must be limited on account of use of visible light.
In contrast, semiconductor lasers are small in size, inexpensive, and yet can be readily modulated, having a longer lifetime than the above lasers. Moreover, since they emit light in the infrared region, the photographic papers spectrally sensitized to the infrared region is suitably used. Such photographic paper can be handled under a bright safelight and has the advantage of more readiness in handling.
On the other hand, it is a well known technique to use a fluorescent brightening agent in order to increase the whiteness of silver halide photographic papers that have been processed.
It is more advantageous to use an oil-soluble fluorescent brightening agent as the fluorescent brightening agent than to use a water-soluble fluorescent brightening agent, in view of the fact that the former fluorescent brightening agent may be flowed out with difficulty in the course of processing.
Incidentally, a silver halide emulsion spectrally sensitized to the infrared region may undergo a serious decrease in sensitivity when an emulsion layer coating solution is prepared and thereafter left to stand. Thus a stable emulsion is advantageous from the viewpoint of the manufacture of light-sensitive materials.
Light-sensitive materials obtained using such an emulsion also have poor storage stability after manufacture, thus having the disadvantage that they are greatly susceptible to desensitization during storage.
Studies made by the present inventors have revealed that such a negative phenomenon is further double strengthened when the fluorescent brightening agent is used for the purpose of increasing the whiteness of photographic papers.